1. Field of the Invention
This invention relates to a method for producing an unstretched seamless tube for use as an intermediate image-transfer belt which is used in the intermediate image-transfer device of an electrophotographic copying machine, a laser printer or the like.
2. Background Art
In a conventional recording apparatus which produces a multicolored image, such as an electrophotographic copying machine, a recording method in which a plastic endless belt is employed as an intermediate image-transfer belt is adopted with a view to avoiding damage to a photoreceptor and obtaining a clear and sharp image free from deviation or fading in color and devoid portions (see Japanese Patent Laid Open Publication No. 2-108072).
In the above method employing a plastic endless belt as an intermediate image-transfer belt, toner images in a plurality of colors are respectively formed on a recording medium such as a photoreceptor, and the toner images thus formed are electrostatically transferred to the intermediate image-transfer belt so that all the toner images can be successively superposed. The toner image thus formed on the intermediate image-transfer belt is then transferred to a recording paper to finally obtain a colored image thereon.
In the above method, as described above, the toner images formed on the photoreceptor are electrostatically transferred to the endless intermediate image-transfer belt. It is therefore important that the belt has a proper degree of electric conductivity.
As a material for an intermediate image-transfer belt having a proper degree of electric conductivity, there has been proposed an electrically conductive resin composition prepared by incorporating an electrically conducting filler such as carbon black into a thermoplastic resin such as a polycarbonate resin or a poly(ethylene terephthalate) resin.
However, as reported in Japanese Patent Laid Open Publication No. 63-311263 an intermediate image-transfer belt made from such a resin composition often exhibits insufficient electric conductivity. Moreover, the conventional belt has various drawbacks such as, for example, uneven electric conductivity due to the poor affinity of carbon black for some types of resins, a rough surface and an insufficient mechanical strength. As a result, an image finally obtained is poor in quality due to deviation or fading in color, or the presence of devoid portions.
Further, as described in Japanese Patent Laid-Open Publication No. 63 311263, the conventional intermediate image-transfer belt is prepared in such a manner that a starting material is first made into a sheet, and then the both ends of the sheet are joined together to form an endless belt. The joint area, which is thicker than the other portion of the belt, has an electric conductivity different from that of the other portion. There is thus another problem in the conventional intermediate image-transfer belt that the joint area cannot be utilized as an image-transfer medium.
It is therefore an object of the present invention to provide a method for the production of a seamless tube, for use as an intermediate image-transfer belt, which has a uniform electric conductivity, a smooth surface and a high mechanical strength.